If you are--or have ever been--involved in alternative diets or vegetarianism, you have probably heard or read claims that comparative anatomy and/or comparative physiology "proves" or (in more conservative language) "provides powerful evidence" that humans are "natural" fruitarians, vegetarians, or even omnivores. This paper will assess such claims and the evidence supporting them, but we first need to ask:

Whether comparative anatomy and physiology provide actual hard proof of the precise composition of the "natural" human diet, or if they merely provide general indications of possible diets.

Then, we want to go beyond the typical simplistic analyses presented in the vegetarian and alternative diet lore, and reexamine what information comparative anatomy and physiology actually provide regarding the natural diet of humans.

Further, a number of related claims are often made as part of such comparative "proofs." Some of these claims addressed here are:

Does "instinct" (whatever that is) "prove" that we are natural vegetarians?

Does research that shows the typical Western meat-based diet is unhealthy prove that all omnivore diets are unhealthy?

And, since it is mentioned in the subtitle, just what is a faunivore, anyway?

If these questions interest you, I invite you along for the ride. But first, open your mind and fasten your seat belt--the ride may be bumpier than you expect!

If your time is limited, or you have specific interests...

As this paper addresses numerous, diverse topics by necessity (some in depth), it is lengthy and this may present obstacles for some readers. Also, considerable background information must be covered before the main claims of the major comparative "proofs" of diet can be addressed.To help navigate the numerous topics, to gain a quick bird's-eye view, or to read the paper in sections as time permits, the comprehensive Table of Contents below provides direct links to all the major sections and subsections of the paper.

T A B L E O F C O N T E N T S

PART 1: Brief Overview: What is the Relevance of Comparative Anatomical and Physiological "Proofs"?

PART 2: Looking at Ape Diets: Myths, Realities, and Rationalizations

PART 3: The Fossil-Record Evidence about Human Diet

PART 4: Intelligence, Evolution of the Human Brain, and Diet

PART 5: Limitations on Comparative Dietary Proofs

PART 6: What Comparative Anatomy Does and Doesn't Tell Us about Human Diet

PART 7: Insights about Human Nutrition and Digestion from Comparative Physiology

PART 8: Further Issues in the Debate over Omnivorous vs. Vegetarian Diets

PART 9: Conclusions: The End, or The Beginning of a New Approach to Your Diet?

Rationalization: The fossil record is irrelevant because we were created, rather than evolved--evolution is nonsense!

Rationalization: Our prehistoric ancestors were acting "against their nature" by eating meat for 2.5 million years!

Rationalization: The evidence of modern ape diets is irrelevant because we are a unique species, and we evolved in a different environment (the African savanna) than the forest-dwelling great apes.

Rationalization: The human gut is far too elastic for comparative anatomy to tell us anything about our natural diet.

Rationalization: The evidence of comparative physiology is irrelevant because: we can get B-12 from unwashed produce; low bioavailability of some nutrients from plants is good because they are toxic except in tiny quantities; physiological measurements made on meat-eaters are invalid!

Rationalization: What happened back in the Paleolithic age doesn't really matter. We are different people today.

Rationalization: Evolution is concerned with reproductive success, not longevity. By the latter measure, vegetarian diets are an improvement on evolution.

Rationalization: Hunter-gatherers may eat some meat but they are not that far from being vegetarians. Plant foods predominate, and animal food is sporadic because hunting is usually unsuccessful/inefficient compared to gathering of plant food.

Rationalization: There are no vegan gatherer tribes because they have not been exposed to the "enlightened" philosophy of veg*nism.

Rationalization: The hunter-gatherer diet is not feasible for people living in modern times.